I have recently purchased a 92 400E with 160.000 miles. My latest problem is running hot while in traffic. Moving down the road it stays at normal temp but when I get stopped the temp raises slowly. If I put the car in neutral and rev the engine, it cools back down. What would be the most likley cause of this?? It appears that the water pump and thermostat have been changed at some time in the past. I have no service records for this car. Appreciate any help you can give. Thanks.....

If it were me, I'd change out the Thermostat and flush and refill the coolant system adding Redline water Wetter.(available at Pep Boys). You say you rev the engine and the temp goes down. Revving the engine spins the Water Pump faster, circulates the water faster and causes the Fan/Clutch assy to suck more air over the radiator vanes. But the Fan/Clutch assy is not primarily what cools the radiator, its the wind blowing through it as the car is being driven. Since the over heating only occurs while being stationary, it doesn't sound like the pump/clutch. Radiator could be clogged due to a poorly maintained cooling system. But really. I'd be looking at the Auxillary cooling fan, as it should be kicking on as the engine temp raises past a critcal value 80 degrees or so

I had a problem like your with a 560 sec and I replaced the thermostat the radiator, the fan clutch etc. and did not make much of a difference until the water pump was replaced. But make sure your auxiliary fans are working.